Sharp LC 20M4U User manual

1
LC-20M4U
SHARP CORPORATION
SY1E1LC-20M4U
LCD AV MONITOR
SERVICE MANUAL
MODEL LC-20M4U
In the interests of user-safety (Required by safety regula-
tions in some countries) the set should be restored to its
original condition and only parts identical to those specified
be used.
Page
»IMPORTANT SERVICE SAFETY PRECAUTION................................................................................. 2
»SPECIFICATIONS ................................................................................................................................ 4
»OPERATION MANUAL ......................................................................................................................... 5
»DIMENSIONS ....................................................................................................................................... 6
»REMOVING OF MAJOR PARTS .......................................................................................................... 7
»ADJUSTING PROCEDURE OF EACH SECTION ............................................................................. 10
»TROUBLE SHOOTING TABLE ........................................................................................................... 13
»CHASSIS LAYOUT ............................................................................................................................. 18
»BLOCK DIAGRAMS ........................................................................................................................... 20
»DESCRIPTION OF SCHEMATIC DIAGRAM ..................................................................................... 22
»SCHEMATIC DIAGRAMS ................................................................................................................... 23
»PRINTED WIRING BOARD ASSEMBLIES........................................................................................ 45
»PARTS LIST
ËELECTRICAL PARTS..................................................................................................................... 50
MAIN UNIT ..................................................................................................................................... 50
JACK UNIT ..................................................................................................................................... 56
INVERTER UNIT............................................................................................................................ 57
SWITCH UNIT................................................................................................................................ 57
ËCABINET PARTS LIST................................................................................................................... 59
ËSUPPLIED ACCESSORIES PARTS.............................................................................................. 59
ËPACKING PARTS ........................................................................................................................... 59
ËCABINET AND MECHANICAL PARTS.......................................................................................... 60
»PACKING OF THE SET ...................................................................................................................... 62
CONTENTS
This document has been published to be used for
after sales service only.
The contents are subject to change without notice.

LC-20M4U
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SAFETY NOTICE
Many electrical and mechanical parts in LCD television
have special safety-related characteristics.
These characteristics are often not evident from visual
inspection, nor can protection afforded by them be
necessarily increased by using replacement components
rated for higher voltage, wattage and etc.
Replacement parts which have these special safety
characteristics are identified in this manual; electrical
components having such features are identified by “ å”
IMPORTANT SERVICE SAFETY PRECAUTION
ËService work should be perfomed only by qualified service technicians who are thoroughly
familiar with all safety checks and the servicing guidelines which follow:
and shaded areas in the Replacement Parts Lists and
Schematic Diagrams .
For continued protection, replacement parts must be
identical to those used in the original circuit.
The use of a substitute replacement parts which do not
have the same safety characteristics as the factory
recommended replacement parts shown in this service
manual, may create shock, fire or other hazards.
WARNING
1. For continued safety, no modification of any circuit
should be attempted.
2. Disconnect AC power before servicing.
TO EXPOSED
METAL PARTS CONNECT TO
KNOWN EARTH
GROUND
DVM
AC SCALE
50k ohms.
10W
0.15 µF
TEST PROBE
•Use an AC voltmeter having with 5000 ohm per volt, or
higher, sensitivity or measure the AC voltage drop
across the resisor.
•Connect the resistor connection to all exposed metal
parts having a return to the chassis (antenna, metal
cabinet, screw heads, knobs and control shafts,
escutcheon and etc.) and measure the AC voltage drop
across the resistor.
All checks must be repeated with the AC cord plug
connection reversed. (If necessary, a nonpolarized
adaptor plug must be used only for the purpose of
completing these checks.)
Any reading of 0.75V peak (this corresponds to 0.5
milliamp.peak AC.) or more is excessive and indicates
a potential shock hazard which must be corrected
before returning the monitor to the owner.
BEFORE RETURNING THE RECEIVER
(Fire & Shock Hazard)
Before returning the receiver to the user, perform
the following safety checks:
1. Inspect all lead dress to make certain that leads are
not pinched, and check that hardware is not lodged
between the chassis and other metal parts in the
receiver.
2. Inspect all protective devices such as non-metallic
control knobs, insulation materials, cabinet backs,
adjustment and compartment covers or shields,
isolation resistor-capacitor networks, mechanical
insulators and etc.
3. To be sure that no shock hazard exists, check for
leakage current in the following manner.
•Plug the AC cord directly into a 110~240 volt AC outlet,
and connect the DC power cable into the receiver's
DC jack. (Do not use an isolation transformer for this
test).
•Usingtwoclipleads,connecta 50kohm,10 wattresistor
paralleled by a 0.15µF capacitor in series with all
exposedmetalcabinetpartsand a knownearthground,
suchaselectricalconduitorelectricalgroundconnected
to an earth ground.
CAUTION
FOR CONTINUED PROTECTION
AGAINST A RISK OF FIRE REPLACE
ONLY WITH SAMETYPE FUSE.
F701 (1.25A, 250V), F702 (1.25A, 250V), F4701
(2.0A, 250V), F4702 (2.0A, 250V) FUSE.
A V

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LC-20M4U
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AVIS POUR LA SECURITE
De nombreuses pièces, électriques et mécaniques, dans
les téléviseurs présentent des caractéristiques spéciales
relatives à la sécurité, qui ne sont souvent pas évidentes
à vue. Le degré de protection ne peut pas être
nécessairement augmentée en utilisant des pièces de
remplacement étalonnées pour haute tension, puissance,
etc.
Les pièces de remplacement qui présentent ces
caractéristiques sont identifiées dans ce manuel; les
pièces électriques qui présentent ces particularités sont
PRECAUTIONS A PRENDRE LORS DE LA REPARATION
ËNe peut effectuer la réparation qu’un technicien spécialisé qui s’est parfaitement accoutumé
à toute vérification de sécurité et aux conseils suivants.
identifiées par la marque “ å” et hachurées dans la liste
des pièces de remplacement et les diagrammes
schématiques.
Pour assurer la protection, ces pièces doivent être
identiques à celles utilisées dans le circuit d’origine.
L’utilisation de pièces qui n’ont pas les mêmes
caractéristiquesquelespiècesrecommandéesparl’usine,
indiquées dans ce manuel, peut provoquer des
électrocutions, incendies, radiations X ou autres acci-
dents.
AVERTISSEMENT
1. N’entreprendre aucune modification de tout circuit.
C’est dangereux.
2. Débrancher le récepteur avant toute réparation.
VERIFICATIONS CONTRE L’INCEN-DIE ET
LE CHOC ELECTRIQUE
Avant de rendre le récepteur à l’utilisateur, effectuer
les vérifications suivantes.
1. Inspecter tous les faisceaux de câbles pour s’assurer
que les fils ne soient pas pincés ou qu’un outil ne soit
pas placé entre le châssis et les autres pièces
métalliques du récepteur.
2. Inspecter tous les dispositifs de protection comme les
boutons de commande non-métalliques, les isolants,
le dos du coffret, les couvercles ou blindages de
réglageetdecompartiment,lesréseauxderésistance-
capacité, les isolateurs mécaniques, etc.
3. S’assurer qu’il n’y ait pas de danger d’électrocution en
vérifiant la fuite de courant, de la facon suivante:
• Brancher le cordon d’alimentation dans la prise CA de
110~240V et le câble d’alimentation CC dans le jack
du moniteur. (Ne pas utiliser un transformateur pour
cet essai.)
• A l’aide de deux fils à pinces, brancher une résistance
de 1,5kΩ10 watts en paralléle avec un condensateur
de 0,15µF en série avec toutes les pièces métalliques
exposées du coffret et une terre connue comme une
conduite électrique ou une prise de terre branchée à
la terre.
• Utiliser un voltmètre CA d’une sensibilité d’au moins
5000Ω/V pour mesurer la chute de tension en travers
de la résistance.
• Toucher avec la sonde d’essai les piéces métalliques
exposées qui présentent une voie de retour au châssis
(antenne, coffret métallique, tête des vis, arbres de
commande et des boutons, écusson, etc.) et mesure
la chute de tension CA en-travers de la résistance.
Toutes les vérifications doivent être refaites aprés avoir
inversé la fiche du cordon d’alimentation. (Si
nécessaire, une prise d’adpatation non polarisée peut
être utilisée dans le but de terminer ces vérifications.)
Une valeur de 0.75V RMS ou plus (correspond à
0.5mA C.A.) est excessive et implique un danger de
secousse électrique, qui devra être supprimé avant
de retourner l'appareil à l'utilisateur.
0.15 µF
SONDE D'ESSAI
VERS PIECES
METALLIQUES
EXPOSEES
VTVM
ECHELLE CA
50K OHMS
10W
CANNECTER A
UNE MASSE DE
TERRE CONNUE
PRECAUTION
POUR LA PROTECTION CONTINUE
CONTRE LES RISQUES D’INCENDIE,
REMPLACER LE FUSIBLE PAR UN FUSIBLE
DE MEME TYPE F701 (1.25A, 250V), F702
(1.25A, 250V),F4701 (2.0A,250V), F4702 (2.0A,
250V).
A V

LC-20M4U
4
SPECIFICATIONS
Items .......................................................... 20" LCD AV MONITOR, Model: LC-20M4U
LCD panel..................................................................................... 20" BLACK TFT LCD
Number of dots .................................................................921,600 (640 x 3 x 480) dots
Low reflection.................................................................................................. Non-glare
Brightness.......................................................................................................430 cd/m2
Viewing angles
Left to right......................................................................................................... 160°
Upper to lower ................................................................................................... 160°
Lamp life ....................................................................... 40,000 hours (at normal mode)
Video color system ..............................N358/N443/PAL/PAL-M/PAL-N/PAL-60/SECAM
Audio amplifier ...................................................................... 4.0 W (0.7 W x 2 + 2.6 W)
Speakers
Full range.......................................................... 1.2 x 1.6 in. (3 x 4 cm) Oval, 2 pcs.
Woofer ............................................................................. 3.1 in.(8 cm) Round, 1 pc.
Terminals
AV 1 IN........................................ Video Composite (BNC type), S-video, Audio R/L
Component input,Y/PB/PR(BNC type)
AV 2 IN/OUT ............................................. Video Composite (BNC type), Audio R/L
Headphone jack..................................................................... 0.1 in. (3.5 mm) φjack
Power supply
DC operation...................................................... DC 13 V, Typical: 3.0 A, Max: 3.8 A
AC operation...........................................AC 110 - 240 V, 50/60 Hz with AC adapter
Power consumption ....................................AC 120V, Typical; 50 W, Standby: 0.5 W
Appearance
Exterior color .................................................................................................... Silver
Outside dimensions ................................................ 18.1 (W) x 17.2 (H) x 7.3 (D) in.
460 (W) x 437.5 (H) x 186 (D) mm
Net weight........................................ 19.0 lbs (8.6 kg), incl. stand, excl. accessories
13.4 lbs (6.1 kg), excl. stand
Accessories
Operation manual ...........................................................Language: English/French/
Spanish/Portuguese
Remote control ....................................................................... Infrared wireless type
(Infrared carrier frequency: 38 kHz)
AC adapter.......................................................................... Multi-Voltage type, 1 pc.
DC cable: 6.5 ft (2 m)
DC power converter: 2.6 (W) x 1.5 (H) x 5.5 (D) in.
(67 (W) x 37 (H) x 140 (D) mm)
AC cord..................................................................................... 6.1 ft (1.85 m), 1 pc.
Batteries............................................. "AAA" size (UM/SUM-4) Dry Battery x 2 pcs.
Cable clamp..................................................................................................... 2 pcs.
OSD language ..........................................................................English/French/Spanish
Specifications are subject to change without prior notice.

5
LC-20M4U
Main unit (rear view)
OPERATION MANUAL
Main unit (front view)
Remote Control

LC-20M4U
6
DIMENSIONS
(Unit: inch/mm)

7
LC-20M4U
REMOVING OF MAJOR PARTS
1. Detach the Rear cover.
2. Remove the Table stand fixing screws (4 pcs.).
3. Remove the Jack PWB fixing screws (9 pcs.) .
4. Remove the Cabinet B fixing screws (5 pcs.).
5. Push on the hook5-1of the Cabinet B to detach, open the cabinet and detach the hooks
from 5-2 〜 5-9 , and then detach the Cabinet B.
6. Peel off the 9 wire holders and 8 tapes, then detach the connecting cords.
7. Detach the connectors from each PWB.
4
3
2
Cabinet B
Table Stand
Stand Cover
Hinge Cover
Table Stand (Cover)
5-7
5-8
5-9
5-6
5-5 5-4
5-3
5-2
5-1
Cabinet A
1
Rear Cover
SC1201
SC1202 SC401
Speaker
(Inverter
PWB)
(Switch PWB)
6
6
Tape
(Main PWB)
6
Speaker Cover (R)
Jack PWB Holder
Speaker Cover (L)
6
6
P4302
P4702
P4001
P1701
P1703
P1702
P1701
P1702
P1771
P4602
SC4402
P4601
P2003
P701
Tape
Tape
Tape
7
7
7
7
7
77
7

LC-20M4U
8
8. Remove the Main PWB fixing screws (4 pcs.).
9. Remove the Inverter PWB fixing screws (3 pcs.).
10. Remove the Jack PWB fixing screw (1 pc.) and Ground fixing screw (1 pc.),
and then remove the Reinforcement plate.
11. Remove the LCD unit fixing screws (2 pcs.).
12. Remove the Switch PWB fixing screws (3 pcs.).
Reinforcement
plate
LCD unit
Main PWB
Jack PWB Ass'y
Switch PWB
Cabinet A
Inverter PWB
12
11
89
10
11
P3204
P3203
10
8
Gasket

9
LC-20M4U
»Precautions in handling the LCD panels
1. Work in a clean room (with humidities below 50%).
2. Be sure to wear an anti-static armband.
3. Handle the panels on an electro-conductive mat.
4. Be careful not to fall, shake and shock the panels.
13. Remove the LCD unit fixing screws (4 pcs.) and
the Rear surface fixing screws (3 pcs.), and then
detach the Shielding plate.
14. Detach the 2 Reflection sheets .
15. Detach the upper and lower Fluorescent lamps.
16. Detach the Light guide plate.
17. Detach the upper and lower Reflection mirrors.
18. Detach the Diffusion sheet and the Reflection
polarising sheet.
Fluorescent lamp (Upper)
(KLMP-0133CEZZ)
Refrection Mirror (Upper)
(PSHEP0223CEZZ)
LCD unit
(RLCDT0060CEZZ)
Fluorescent lamp (Lower)
(KLMP-0134CEZZ)
Refrection Mirror (Lower)
(PSHEP0224CEZZ)
Diffusion sheet
(PSHEP0179CEZZ)
Light guide plate
(PGiDM0058CEZZ)
Reflection polarizing sheet
(PSHEP0216CEZZ)
Reflection sheet-2
(PSHEP0187CEZZ)
13
13
14
15
18 17
15
17
16
Reflection sheet-1
(PSHEP0186CEZZ)
Shielding plate
(PSLDM4712CEFW)
LCD unit
(Front surface)
13
13

LC-20M4U
10
ADJUSTING PROCEDURE OF EACH SECTION
When the microprocessor (IC2001) or the E2PROM (IC2004) has been replaced or when the E2PROM has been initial-
ized, it is necessary to readjust the microprocessor. Below discussed is the adjustment procedure.
Preparations
Use a dedicated AC adapter or a regulated DC power supply.
AC adapter :UADP-0220CEZZ
DC power supply :13 V, 3.8 A
Use also a SHARP TV remote controller.
1. Adjustment procedure
Power on (initialization) →Adjustment process mode (remote controller) →+B adjustment →
Counter bias adjustment →White balance adjustment →Performance check →Factory settings
Calling the adjustment process mode
There are the following two ways to enter this mode.
●Turn on the power and press the “ADJUST PROCESS” key on the remote controller.
●While holding either KEY4 (pin (81) of the microprocessor) or KEY5 (pin (82) of the microprocessor) at the “L” level,
turn on the power.
Using the keys for the adjustment process
Selecting an adjustment item and adjusting its setting
●Using the menu button (M key), select an item, and using the VOL+/- buttons, adjust its setting.(The menu button
serves as a toggle switch. New settings entered with the VOL buttons are made effective immediately.)
Other key-in behaviors
●The input select key serves also as a toggle switch.
The input is switched from AV1 to AV2.
●Press the auto preset button on the remote controller in the adjustment process mode, and the top item of the next
page will show up regardless of which item appears now.
Page 1 →Page 2 → ...... →Page 6 →Page 1
●Press the manual memory button on the remote controller in the adjustment process mode, and the top item of the
same page will show up.
1-1. Initialization
Ground the pins (81) and (82) of IC2001 (microprossor) and turn on the power.The unit will be initialized and then
enter the adjustment process mode.
Select M4U in the MODEL item. Adjustment process page 1.
Select 20 in the INCH SIZE item. Adjustment process page 1.
Turn off the power and get the pins (81) and (82) of IC2001 (microprossor) back to their original state.
* Before turning off the power, quit the adjustment process mode with the remote controller. If unavoidably
the power must be switched off directly, wait at least 5 seconds after making the settings.
1-2. +B adjustment
Feed the standard NTSC color bar signal.
Enter the adjustment process mode.
Adjust the “+B-ADJ” setting on the adjustment process page 1 so that the voltage at pin (5) of P2001 should be
5.00 ±0.02 V.
Note: Make the 5.0V adjustment as exactly as possible because this voltage this voltage will be reference level for all
the supply voltages.

11
LC-20M4U
1-3. Counter bias adjustment
Keep off the video input signal.
Place the specified tool at the center of the screen.
Observe the output of the tool on the oscilloscope screen.
Adjust the “COM BIAS” setting on the adjustment process page 2 so that the peak-to-peak level of the waveform
should be minimum.
1-4.White balance adjustment
Feed the NTSC monoscope pattern signal.
Adjust the “RCUTOFF” and “BCUTOFF” settings on the adjustment process page 2 so as to obtain the color of the
same level as the standard monitor.
Note: For the “RCUTOFF”and“BCUTOFF” settings, keep the readings in the range of -9 to +9.If out of this range, the
user-adjustable range is reduced.
Adjust them in the indication value range of -9, -7, -5, -3, -1, +1, +3, +5, +7, +9 (odd numbers).When it becomes
even-numbered value (include 0), side favor noise sometimes occurs in the monochrome signal of the specific
gradation.
Do not change the “GCUTOFF” settings (It also change the black level).
1-5. Factory setting
Set the product’s input mode, picture quality and other factors to their factory setting.
There are the following two ways.
●With the keys of the set
In the inspection process mode, hold down both the “SELECT(▲)” and “VOL (+)” buttons of the set until “SETTING
COMPLETE” appears on the screen.
Note: Be careful not to turn off the power, release the above two keys and press any other keys until “SETTING
COMPLETE” appears on the screen.
●With the adjustment remote controller
With the adjustment remote controller, make the factory settings. Either of the following remote controllers codes
will do.
Calling the Inspection process mode
There are the following two ways.
●With the keys of the set
Hold down the “MENU” and “AV INPUT” buttons of the set and turn on the power.
●With the adjustment remote controller
Use the inspection process key.
Key name Remote controller code
Factory setting 100000111111110
Factory setting 100000001010110
E
Changing on-screen display
K
Inspection process mode Factory setting Setting complete
SETTING COMPLETE
→
→
E

LC-20M4U
12
1
>+B–ADJ 160
MODEL M4U
INCH SIZE 20
TIMER 1
SYSTEM AUTO
NTSC PWM FREQ 0C0
PAL PWM FREQ 0B0
TV GAIN OFF
ERROR NO RESET 0
PMUTE 00
PUBLIC MODE ON
COLOR SW
20M4 VER 1.000
Adjustment process
settings
Microprocessor
version
Adjustment process
items
Adjustment process page number
2. Lamp error detection
Function
For added safety, this LCD colorTV set has the lamp error detection.The power is automatically turned off if the lamp
or its circuit gets in trouble.
If by any chance there is a problem with the lamp or its circuit, or if the lamp error detection function is activated for any
other reason, the set behaves itself as follows.
1Even when you switch on the power, the set turns itself off in about 5 seconds.(The power LED indicator on the
front of the set turns from green to red.)
2If the above action 1occurs 5 times consecutively, the set cannot be switched on.(The power LED indicator stays
in red.)
Correction
●Checking with the lamp error detection circuit off
If the lamp error detection fuction is activated to turn off the power LED indicator turns red and the set is now in the
adjustment process mode.In this state, the error detection circuit gets disabled and the power is turned on again.
In so doing, the lamp and its circuit can be checked for anything unusual.
Check to see if “1” or higher value appears in the “ERROR NO RESET” box in the 9th line of the adjustment
process page 1. If so, a lamp error has been detected.
●Resetting the lamp error counter
Finally make sure the lamp and its circuit are error-free, and reset the lamp error counter.To do so, select the
“ERROR NO RESET”box in the 9th line of the adjustment process page 1 and enter “0” with theVOL button.
Do the performance check and make sure the lamp error detection functions is not activated.
3. Precautions in making adjustments
In making adjustments, keep the following points in mind.
●When you have modified the MODEL and INCH SIZE settings on the process page 1, never turn off the power in
at least 5 seconds.It takes this time to write the E2PROM for all the adjustment process parameters of a different
mode.(The cursor does not move for a few seconds when the writing is going on.) If you have wrongly turned off
the power, once change the MODEL setting to any other model number, wait for 5 seconds, and change the setting
back to the right model number.Then wait for another 5 seconds just to be sure.
●To quit the adjustment process mode with adjustments complete, use the ADJUST PROCESS key on the remote
contoller.
4. Adjustment process items

13
LC-20M4U
TROUBLE SHOOTINGTABLE
No picture, No sound
Check all the settings microprocessor's adjust process menu.
Do F701 function?
Are T701's secondary outputs, +34V, +15V, +10V, +5V and -9V normal?
Remove F701 and check the load side. Is there short-circuiting?
Is there short-circuiting of T701 primary side periphery, Q701, Q703 and S4001?
Replace F701.
Check S4001 and connection cable.
Is T701's primary oscillator waveform normal?
Check T701's secondary load.
Yes
No
No No
No
Yes
Fluorecent lamp failure to light up
Does F4701 and F4702 function?
Is the pin (34) of IC1201 in the "H" state?
Is the Q1774 short-circuiting?
Is there short-circuiting of T1701~T1706 primary side periphery, Q1701~Q1705?
Yes
Yes
No
No
No
Yes
Replace the fluorecent lamp with new one and check again.
Yes
Check the OFL1 line, IC1201 and their peripheral parts.
Check Q1774 and its peripheral parts.
Check T1701~T1706, Q1701~Q1705 and connection cable.
No
Replace F4701 and F4702.
Yes

LC-20M4U
14
TROUBLE SHOOTINGTABLE (Continued)
No picture
Check all the settings microprocessor's adjust process menu.
Is in/output of IC801 normal?
Is in/output of IC1201 normal?
Check IC801 and its peripheral parts.
Check IC1201 and its peripheral parts.
Check IC402 and its peripheral parts.
Check IC801, AV1 line and its peripheral parts.
Check LCD panel voltage and waveform.
Yes
Yes
No
No
No picture at all
Is in/output of IC402 normal?
Is input at pin (73) of IC801 normal?
Yes
No
No
No VIDEO 1 and VIDEO 2 output
Is input at pin (1) of IC402 normal?
Is the pins (2) and (4) of IC402 at "L" state?
Check the its line. Check the its line.
Check IC402 and its peripheral parts.
Is the pins (65) and (66) of IC2001 at "L" state?
Yes
No
No
Yes
Yes
No VIDEO 1 output
Is input at pin (5) of IC402 normal?
Is the pin (4) of IC402 in the "H" state?
Check the its line. Check the its line.
Yes Yes
No
No
No VIDEO 2 output
Check IC402 and its peripheral parts.
Is the pin (68) of IC2001 in the "H" state?
No picture
Check all the settings microprocessor's adjust process menu.
Is input at pins (71) and (72) of IC801 normal?
No S-VIDEO output
Check SC401, SY-line, SC-line and their peripheral parts.
No
Is input at pins (4), (5), (6) and (75) of IC801 as specified?
No COMPONENT output
Check J4403, J4404, J4405, DVD-Y line, PB line, PR line and their peripheral parts.
No

15
LC-20M4U
No picture
Check all the settings microprocessor's adjust process menu.
Is source GND normal?
Is CSCOM waveform normal?
Check R1212 and its peripheral parts.
Check IC1109, Q1101, Q1102, D1101, R1120, R1130 and their peripheral parts.
Check R1231 and its peripheral parts.
Yes
No
No
Becomes dark
No
Time passes, becomes dark
Is gate GND normal?
Is gate clock (GCK) normal?
Is output at pin (3) of IC1205 normal?
Yes
No
Check D1201 and its peripheral parts.
No
Is B-5.5V being outputted?
Is VCC being outputted?
Check T701's secondary +5V outputs line.
Yes
No
Is GSP waveform normal?
Check R1223 and its peripheral parts.
Yes
No
Check R1223 and gate array peripheral parts.
Becomes white.
Is 3.3V VSH being outputted?
Is source clock (CK) normal?
Check +3.3V outputs line of IC781.
Check R1210, R1211 and their peripheral parts.
Check FB1203 and gate array peripheral parts.
Is output of LBR and HG normal?
Yes
Yes
No
No
No
Vertical line output
TROUBLE SHOOTINGTABLE (Continued)

LC-20M4U
16
No picture
Check all the settings microprocessor's adjust process menu.
Is output of R0~R5 normal?
Is output of G0~G5 normal?
Is output of B0~B5 normal?
Check R1202, R1203 and their peripheral parts.
Check R1204, R1205 and their peripheral parts. Check R1206, R1207 and their peripheral parts.
Check T701's secondary +5V outputs line.
Yes
Yes
No
No
No
Color is unusual
Is VLS 5V being outputted?
No
Picture image is gloomy
Is in/output of SPIO and SPOI normal?
Check R1209 and its peripheral parts.
No
No picture image inversion
Is output V0, V16, V32, V48 and V63 normal?
Check IC1106, IC1107, IC1108 and their peripheral parts.
No
Gradation defect
Is output of U/D normal?
Check Q1201 and its peripheral parts.
Yes
No
TROUBLE SHOOTINGTABLE (Continued)

17
LC-20M4U
No sound
Check all the settings microprocessor's adjust process menu.
Is pin (53) of IC2001 at "L" state?
Are outputs at pins (1) and (7) of IC903 as specified?
Are inputs and outputs of IC303 as specified?
Yes
Yes
No
No
No
No
No sound from front speakers
No sound from rear speakers
Are inputs at pins (5) and (8) as well as outputs at pins (2) and (11), all of IC301, as specified?
Yes
Muting effect is on. Check the FSMU line.
Check IC901, IC903 and their peripheral parts. Check IC303 and its peripheral parts.
Check the line in question. IC303 and its peripheral parts.
Check RY351, speakers and their peripheral parts.
Yes
Is pin (54) of IC2001 at "L" state?
Are input at pin (5) as well as output at pin (2) of IC302 as specified? Check the speaker and its peripheral parts.
Yes
Yes
No
No
Muting effect is on. Check the FSMU line.
Check the line IC901, IC303 and their peripheral parts.
No sound from headphone
Is pin (55) of IC2001 at "L" state?
Check the headphone and its peripheral parts.
Check Q371, J4001 and their peripheral parts.
Yes
No No
No sound from output line
Is pin (52) of IC2001 at "L" state?
Are output at pin (1) and (7) of IC902 as specified?
Check the LMUTE line.
Check IC902, and its peripheral parts.
Yes
No
Check the line in question.
Yes
TROUBLE SHOOTINGTABLE (Continued)

18
LC-20M4U
A
B
C
D
E
F
G
H
I
J
12345678910
CHASSIS LAYOUT
MAIN Unit (Side-A)
MAIN Unit (Side-B)

19
LC-20M4U
A
B
C
D
E
F
G
H
I
J
12345678910
JACK Unit
INVERTER Unit
SWITCH Unit

1234567891011 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
H
I
J
LC-20M4U LC-20M4U
BLOCK DIAGRAM
VIDEO IN
AUDIO L/R IN
PY IN
AV1
IN
POWER IN
DC 13V
VIDEO IN/OUT
AUDIO L/R
J4401
J4303
J4403
PB IN
J4404
PR IN
J4405
IN/OUT
AV2
IN/OUT
J4402
J4302
MSP
MUTE
MUTE
VPC
BUFFER
IN/OUT
SELECTOR
IC351
IC902
IC901
HEAD PHONE
J4001
J4701
LPF
L/R
AUDIO AMP
REVERSE
FRONT SPREAR SP
AUDIO AMP
FRONT SP
FRONT SP
REAR SP
PY.PB.PR
AV1
VIDEO SELECTOR
IC402 I2C
LCD
CONTROLLER
IC1201
FIFO
IC1202
Y/C
CLOCK.H/VSYNC.FIELD LCD
PANEL
R.G.B CONTROL SIGNAL
IC1102
IC1103
IC1104
IC1105
IC1106
IC1107
IC1108
IC1109
IC1110
GRADUATION
POWER FOR
LCD
COMMON
DAC IC1101
MPU
IC2001
I2C
CONTROL SIGNAL
SYNC
SEPARATION
VOUT
IC801
SYNC
75ohm BUFFER
Q453
Q454
AGND
IN/OUT
E2PROM
IC2004
RESET
IC2002
5V Reg
IC2701 5V
IC701
PWM
DC/DC
TRANS
T701
5V
38V
16V
9V
-8V
3.3V Reg
IC781 3.3V
29V
8V
Q704
Q7306
IC702
LAMP
DC/AC
TRANS
INVERTER
DRIVE
TR
Q1702
Q1703
LAMP
CHECK
LAMP GND
DC12V
R/C
RECEIVER CONTROL KEY
BRIGHTNESS
PULS
IC903
IC302 IC301
IC303
IC401
SW PWB
JACK PWB MAIN PWB
LCD UNIT
I2C
YC IN
SC4401
SSW
SSW
SC
SY
SYSC
INVPWB
DC12V
CONTROL SIGNAL
RELAY RY351
PWB GND
PANEL SHELD
PWB GND
PANEL SHELD
PWB GND PANEL SHELD
PWB GND
PANEL SHELD
GASKET
QEARZ0017CEZZ
WIRE
QCNW-A272WJZZ
QCNW-
A268WJZZ
QCNW-
A269WJZZ
FFC
FFC
WIRE
QCNW-
WIRE
QCNW-A271WJZZ
WIRE
QCNW-5372CEZZ
FFC
QCNW-
A270WJZZ
A271WJZZ
SCREW
SCREW
RCORF
A005WJZZ
6dB
5V
I2CSC OUT
SY OUT 3.3V Reg
2.5V Reg
2.5V Reg
IC7701
IC7702
IC7102
AV IN
3-DY/C
SEPARATION
IC7001
Q1704
Q1705
T1701
T1702
T1703
T1704
T1705
T1706
IC7201
20~21